The present invention relates to control means for a gripper shuttle in which the shuttle is picked alternately from both sides of the loom. Each side of the loom has a shuttle box for receiving the shuttle and a picking mechanism for propelling the shuttle to the opposite side of the loom.
The invention is particularly directed to gripper shuttle looms in which the shuttle box is rotated 180.degree. after receiving the shuttle. This type of loom is shown in the following U.S. patents to V. Svaty: U.S. Pat. Nos. 3,315,709 dated Apr. 25, 1967 and 3,330,305 dated July 11, 1967 and U.S. patent to Rambousek 3,875,974 issued Apr. 8, 1975. In the type of loom disclosed in each of these U.S. patents, the gripper shuttle enters the shuttle box and is checked or braked. The shuttle is positioned within the shuttle box to a predetermined picking and threading position. The filling which has been brought across the loom from the opposite side thereof, is disengaged from the shuttle gripper and a new filling is inserted into the shuttle gripper. The shuttle box is mounted on a turntable which is rotated 180.degree. after the new filling has been inserted into the gripper so that the shuttle is turned 180.degree. with the head of the shuttle pointed towards the end from which it came. Before rotation of the shuttle box, the braking or checking mechanism is released from its checking function on the shuttle and the shuttle is guided so that it remains in the picking position. After the shuttle box has been rotated to the second position, the shuttle is picked out of the shuttlebox. See, for example, the braking mechanism disclosed in the Svaty et al U.S. Pat. No. 3,487,860 dated Jan. 6, 1970.
In looms of the gripper shuttle type, the shuttle must be precisely positioned at a predetermined location for a threading operation and for accurate picking out of the shuttle box. If the shuttle is not precisely positioned for picking, the amount of force transmitted to the shuttle by the picking mechanism will vary and this results in an inaccurate shuttle flight. If the picking force is insufficient to propel the shuttle completely through the warp shed to the opposite side of the loom, the lay will trap the shuttle in the warp shed. It is well known in the weaving art to positively position a shuttle that has been received into the shuttle box, so that it is in a predetermined position for threading and picking. Shuttle positioning means are shown for example, in the above described patents to Svaty and Rambousek. However, the mechanism for braking or checking the shuttle and for positioning the shuttle must be disengaged from the shuttle before the time of picking. In the case of a rotating shuttle box, the braking mechanism must be released before rotation of the shuttle box. During the time period between release of the braking mechanism and picking of the shuttle, there exists the possibility of the shuttle being moved out of the predetermined picking position by external forces, such as loom vibration and the tension exerted by the filling in the shuttle gripper. In the prior art looms, means are provided for guiding the shuttle as the shuttle box rotates so that the shuttle remains in the predetermined picking position. However, the shuttle can only be guided until the shuttle box reaches the second position to allow the shuttle to be picked. Therefore, when the shuttle box is in the second position, there is a tendency for the shuttle to be pulled away from the picking mechanism. The type of loom to which the present invention is particularly directed, as shown in the Svaty patents, supra, includes means for picking the shuttle. The picking means comprise a piston to which is attached a picking member that engages the end of the shuttle. If the shuttle is not properly positioned close to the end of the picking member, the end of the shuttle will be struck abruptly, thereby producing a high initial acceleration which causes the filling to break.
The problem resulting from the lack of control of the shuttle during the period just prior to picking of the shuttle have been partially solved by the control mechanism shown in U.S. patent to Osgood U.S. Pat. No. 4,108,215 issued Aug. 22, 1978. In this patent, a biased restraining member is located along the groove of the shuttle box in which the shuttle is slidingly guided. The restraining member employs a braking force to the shuttle as long as it is in the shuttle box. This braking force is sufficient to maintain the shuttle in the desired picking position, but does not prevent the shuttle from being picked out of the shuttle box. Although the mechanism shown in the Osgood patent performs satisfactorily when it is first installed, after a short period of time, the problems that it was intended to solve begin to re-appear. A variety of loom malfunctions occur. The problem is compounded by the fact that it is not readily apparent that the malfunctions are caused by a loss in effectiveness of the restraining member, therefore, as the restraining member begins to fail it creates a severe diagnostic problem for the loom fixer. Even when the restraining member is suspected as being the source of a problem, that fact cannot be completely determined until the faulty restraining member is replaced by a new one. Upon examining the faulty restraining member, its ineffectiveness appears to be due to either excessive wear of the member or a fracture in the member or the biasing means which urges the member against the projectile when it is in the groove of the shuttle box. These and other difficulties experienced with the prior art devices for looms operating with rotating shuttle boxes have been obviated in a novel manner by the present invention.
It is, therefore, a principal object of the invention to provide a shuttle control apparatus which maintains the shuttle in a predetermined picking position until the time of picking without interfering with the picking of the shuttle out of the shuttle box.
Another object of this invention is the provision of a shuttle control apparatus which applies a restraining or braking force to the shuttle only after the shuttle box has been rotated to its second or picking position.
A further object of the present invention is the provision of a shuttle control apparatus in which the restraining force on the shuttle is maintained for only a brief period of time at the beginning of the picking stroke.
It is another object of the instant invention to provide a shuttle control apparatus which is simple in operation, reliable and capable of a long life of useful service.